In silicon single crystals manufactured by a Czochralski (CZ) method, there are defects called grow-in defects such as an FPD (Flow Pattern Defect), an LSTD (Laser Scattering Tomography Defect), a COP (Crystal Originated Particle), and the like, they can be a factor which degrades device characteristics, and hence importance is given to a reduction in these defects.
With the aim of describing these defects, a description will be first given as to generally known facts about a vacancy type point defect called vacancy (which will be referred to as V hereinafter) and an interstitial type silicon point defect called interstitial-Si (which will be referred to as I hereinafter) which are taken into a silicon single crystal.
In a silicon single crystal, a V region means a region which has many concave portions or hole-like portions which are produced due to insufficiency of silicon atoms, and an I region means a region which has many dislocations or lumps of superfluous silicon atoms produced when silicon atoms are superfluously present. In particular, it is known that the grown-in defects such as FPDs, LSTDs, and COPs produced in the V region are a factor which degrades oxide dielectric breakdown voltage characteristics in a device process. Further, a neutral region (which will be referred to as an N region hereinafter) which has no (less) insufficiency or superfluousness of atoms is present between the V region and the I region. Furthermore, it is known that the grown-in defects (FPDs, LSTDs, COPs, and the like) are produced consistently when V or I is supersaturated, and that no grown-in defect is present when atoms are saturated or less even though the atoms are slightly biased.
Moreover, it has been confirmed that defects called OSFs (Oxidation Induced Stacking Faults) are distributed in a ring-like form near a boundary between the V region and the I region when seen in a cross section vertical to a crystal growth axis (a region where OSFs are produced will be referred to as an “OSF region” hereinafter). Additionally, it is known that these defect regions change depending on, e.g., a pulling rate at the time of growing a crystal.
As a method for evaluating the grown-in defects, a method which uses a heat treatment or an oxidation treatment like Patent Literature 1 or Patent Literature 2 or a method which uses etching like Patent Literature 3 is general. Further, as a method for determining a defect region, especially the N region, a method for performing the oxidation treatment like Patent Literature 4 is known, and a method combined with a Cu deposition method is also known.
Furthermore, like Patent Literature 5,a method for manufacturing a silicon single crystal having a desired defect region like a V region or an N region by adjusting manufacturing conditions such as an in-furnace temperature at the time of manufacturing a single crystal has been also suggested, but the manufacturing conditions required for the N region are particularly difficult, and stable products are hardly provided. Thus, even in case of manufacturing a single crystal by such a method, determining a defect region as a quality inspection is important.